The object of the present invention, as shown by its title, is related to a device for separating, lifting and transporting sheets of aluminium or other non-ferromagnetic material as shown by its name used for feeding cutting and ironing lines, aluminium component transfer lines, etc.
When dealing with a pile of sheets and trying to lift the top one with the help of a vacuum system it is often the case that, due to the adherence of the sheets, several are lifted at a time.
In iron or ferromagnetic sheets this problem has been solved by putting magnets on the sides of the piles of sheeting, which separate the edges of the top sheets. Thus, with a slight separation between the sheets, even if only at the edges, when vacuumed, only the first sheet is picked up and not the others.
If one wishes to work only with non-ferromagnetic sheets, this problem cannot be solved by magnets alone, since they are not at all magnetised, so it is necessary to use mechanical solutions which encumber the manipulation of said sheets and generally lower performance of the installations for manipulating and transporting sheeting, and therefore the performance of all processes that follow.
In order to eliminate the aforementioned drawbacks, the device for separating, lifting and transporting sheets of aluminium or other non-ferromagnetic material has been developed. Said device is based on the physical fundament of Lorentz force. This force is manifested in electrically charged particles that move and, the magnetic field which said particles are within, according to the corkscrew law. Its mathematical expression is F=qxc2x7(vxc3x97B), where q is the electrical charge, v its velocity, and B the magnetic field at the point where the charge is located.
A metal is a medium where electrons can circulate relatively easily, that is, a large amount of current can be sent through with a moderate or very small Joule. Therefore, if we make a small electrical current (electrically charged particles in movement) pass through a thin metal sheet in a certain direction and apply a magnetic field perpendicular to the direction of said electrical current and coplanar to the surface of the sheet, we generate a force of attraction directed towards the direction perpendicular to the sheet. This perpendicular force is that which will make the sheet lift.
Putting this observation into practice, if we make an electrical current circulate, with metallic electrodes, in the surroundings of the two longer sides of a rectangular shaped metal sheet, while at the same time, by way of permanent magnets we provoke a magnetic field between the contact electrodes, we generate forces of attraction on the aluminium sheet that provide the lifting of said sheet.
The electrical current is distributed all around the sheet, but there are areas where it circulates more intensively than others, specifically along the imaginary lines that join the contact points with the electrodes, reaching the highest values at these very points and consequentially, it is where more force of attraction is generated on the sheet.
According to the theoretical principle shown above, and the practical observations made, the device for separating, lifting and transporting sheets aluminium or other non-ferromagnetic materials is made up of a spider attraction assembly and the electrical supply system.
The spider attraction assembly is a rectangular metal housing, made of any non-ferromagnetic material, of dimensions similar to those of the aluminium sheeting that it will be manipulating. On the two longer sides, a series of blocks of magnets are arranged in linear fashion; at the beginning and the end of the row of blocks of magnets said spider assembly is provided with two retractable cylindrical metal electrodes (which retract when they are pressed on the sheet of aluminium) that end in a square, flat surface of 30 to 50 mm. sides in order to improve transmission of the electrical current.
The blocks of magnets are made up of a number of magnets between 8 and 12 encapsulated by a metal box, preferably iron, leaving a strip uncovered over the union of two magnets generating a magnetic flow in the same direction in all the blocks. Said blocks of magnets have a width of between 50 and 70 mm., a length of between 60 and 120 mm. and the stack thickness of between 30 and 60 mm.
The rectified electrical current supply system is able to supply electrical currents between 100 and 500 A and power between 1,200 and 1,500 W.